A cutter-bar drive is described in East German patent 227,870 which can be mounted as a unit at any location on the intake trough of a field harvester. It has in the center of its frame underneath the intake trough a blade drive that can be mounted as two separate halves between the struts of the frame. A drive shaft carrying an eccentric disk is carried on the two halves. Cranks connected to the eccentric disk are fitted with connecting rods that are pivoted on L-shaped levers whose free ends are in turn pivoted on the blade bars. Thus rotation of the eccentric oppositely reciprocates these blade bars.
Such a blade assembly has the disadvantage that it vibrates considerably, generating substantial throw because of the codirectional movement of most of its parts. The machine therefore generates considerable noise. Furthermore the bearings for the L-shaped actuating arms are subjected to substantial wear, and any vertical displacement of the blade bars, as for instance when they engage a rock or wire, puts substantial stress on the assembly. In addition the small actuating arms must be specially coupled to the blade bars as their ends attached to these arms describe arcs as the arms oscillate, and the bars must move primarily in a straight line. The result is substantial wear of the backs of the individual blades and the lateral guides for the blades must be relatively loose, thereby encouraging the generation of more noise.
In East German patent 216,458 another blade-assembly drive is described which is aimed at extremely wide-mouth machines. A power takeoff shaft behind the cutter trough is connected on both sides to connecting rods connected via angle arms to the blade bars. These arms extend outside past the sides of the machine where they can be fouled with crop. Once again this machine generates considerable noise and vibration.